The present invention relates to the field of radio communication systems. In particular, the present invention relates to portable and/or mobile radios.
Portable and mobile radios are normally arranged to communicate with one another through a base station. The radios and the base station are referred to as a Personal Mobile Radio (PMR) system. Several base stations may be linked together to form a network. A radio can therefore communicate with any other radio which is within communication range of one of the base stations of the network.
Some PMR radios are capable of communicating with other radios directly, without the communication passing through a base station. This mode of operation is referred to as Direct Mode Operation.
FIG. 1 illustrates the general scheme of a PMR radio system 10. Portable radios 2, 4 and 6 of FIG. 1 can communicate with a base station 8. Radios 2, 4 and 6 could equally well be mobile radios mounted in vehicles. Each of the radios shown in FIG. 1 can communicate through base station 8 with one or more other radios. If radios 2, 4 and 6 are capable of direct mode operation, then they may communicate directly with one another or with other radios, without the communication link passing through base station 8.
Portable and mobile radios are also known which can place calls to telephone subscribers. These calls may be from the radio to either a xe2x80x98POTSxe2x80x99 landline telephone, or a mobile telephone.
There are therefore various communications options available to the operator of a portable or mobile radio.
There is a need to make operation of the portable or mobile radio simple. This, for example, reduces the time required for a user to set up a call to another radio or a telephone subscriber. This may be of particular advantage to public safety users of portable or mobile radios.
Simplification of the actions to be carried out by the user also reduces the user""s likelihood of making mistakes. Finally, this simplification also saves money for users of radio systems, since it reduces the amount of training which must be provided to users of the radios.